The present invention relates to a system for dividing a video signal outputted from a television camera into blocks to effect a bandwidth compressive coding based on a predictive coding or code transform scheme.
An example of such a predictive coding system is disclosed in U.S. Pat. No. 4,460,923. The predictive coding system comprises a scan converter in which a plurality of blocks are formed to convert an input video signal into a block formation video signal, a subtractor to make the difference between the block formation video signal suitably delayed and a prediction signal from a prediction signal generator to be referred to soon to generate a prediction error signal, a quantizer to limit the number of possible levels of the prediction error signal, and a code compressor responsive to the quantized prediction error signal from the quantizer to generate compressed information which will be transmitted to a transmission path. The predictive coding system further comprises an adder for adding the quantized prediction error signal to the prediction signal to generate a locally decoded signal, the prediction signal generator operative to generate a prediction signal by using the delayed local decoding signal and in accordance with information signifying an optimum prediction function (motion vector) supplied from an optimum prediction detector. Thus, the above-mentioned predictive coding system makes it possible to determine a motion vector in accordance with both motion vector information and prediction error information, thereby providing a remakably improved coding efficiency especially where the transmission speed is low. Accordingly, such a predictive coding system is especially effective where a television signal undergoes compressive coding and is transmitted at a low speed.
Ordinarily, the coding system of this kind effects code conversion in block units defining a picture frame. Namely, such a coding system is configured to determined the number of lines to be included in each block so that a muiltiple of integer of a predetermined number of lines for each block unit is equal to the number of scanning lines of a picture frame to transmit the first block position information including picture frame synchronization position information and information regarding which line within the first block position information corresponds to a synchronization position of the picture frame.
However, the drawback with the conventional system for coding video signal in block unit is as follows. For instance, when an NTSC color television signal having 525 scanning lines within a picture frame is employed, a predetermined line number defining a block unit is limited to the value selected from 3, 5, 7, 15 and 25 etc. For this reason, irregular processing is required in the configuration of hardware. Attention is drawn to e.g. a system provided with two cameras operative asynchronously with each other. In case where one camera A is switched to the other camera B, when the line number within the last block of the picture frame given by the camera B is different from that within the last block of the picture frame given by the camera A, a particular hardware for processing this is required.